U.S. Pat. No. 3,815,416, assigned to the assignee of this patent application, discloses a prior art apparatus for indicating the level of liquid in a tank. The patented apparatus comprises a float encircling a tube extending down into the tank. The float is magnetically coupled to a gauging rod which bears indicia representing the level of liquid in the tank. As the liquid level rises, the float carries the rod upwardly. The tankerman is apprised of the level in the tank by the visible indicia of the rod. The patented apparatus also has a mechanism for automatically visually and audibly alerting the tankerman when the level has reached a particular level, such as near full. This mechanism includes a tower and a series of reed switches mounted on the tank above the rod opening. A magnet attached to the top of the rod would come into close proximity to the reed switches to serially actuate them as the tank is becoming filled.
While this system performs quite well, the tower is undesirable because it adds expense to the apparatus, is more dangerous and is cumbersome.